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Chapter 05Lecture and Animation

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Integumentary System

Chapter 5-Integumentary System

• What does integument mean?

covering

• Components– skin– hair– nails– glands

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Subcutaneous tissue(hypodermis)

Skin

Dermis

Epidermis

Hairs

Adipose tissueSweat gland

Artery

Vein

Nerve

Hair follicle

Arrector pili(smooth muscle)

Sebaceousgland

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Skin

Epidermis Dermis Hypodermis

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Functions

1. Protection:

water loss, microbes, UV light

2. Sensation:

hot, cold, pain, pressure

3. Temperature regulation:

helps maintain homeostasis

4. Excretion:

removes waste

5. Vitamin D production:

UV light stimulates production

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Skin Facts

• Weighs 9 lbs.

• Used to determine body fat

• 2 main regions: epidermis and dermis

Skin of Finger

Epidermis DermisThin Skin

Thick Skin

EpidermisEpidermis

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Epidermis• 1st major skin region (outside)

• Composed of stratified squamous epithelium

• Keratinization:

- process in which new cells (with keratin) push

old cells to surface

- 40-56 days for new cells to reach surface

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Strata of Epidermis• Stratum corneum:

- outermost layer of epidermis

- 20-30 layers of dead squamous cells filled with keratin

- accounts for 75% of epidermal thickness

- dandruff is this layer flaking off scalp

• Callus:

forms when stratum corneum has frequent friction

SkinLow Magnification

Epidermis

Dermis

Dermal papillae

Duct of merocrine sweat gland

Stratum corneum

Stratum granulosum

Stratum spinosum

Stratum basale

SkinHigh Magnification

Epidermis

DermisStratumbasale

Stratumspinosum

Stratumgranulosum

Stratumcorneum

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• Stratum basale:

- deepest layer of epidermis

- single layer of cells

- firmly attached to dermis

DermisDermis

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Dermis• 2nd major skin region

• Dense connective tissue

• Contains collagen and elastic fibers

• Contains fibroblasts, nerve endings, smooth muscle, glands, blood vessels, and hair follicles

• Cleavage lines:

- area where skin is most resistant to stretching

- due to orientation of collagen fibers

- important in scarring

Dermis and Dermal Papillae

Dermis Dermal papillae

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Layers of Dermis

• Papillary layer:

- thin connective tissue layer that contains blood

vessels

- Dermal papillae:

- projections that extend up into epidermis

- remove waste and help regulate body temp.

- ridged on hands and feet (fingerprints)

- pattern is genetically determined

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• Reticular layer:

- deepest layer of dermis

- accounts for 80% of dermis

Hypodermis

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Hypodermis• Below dermis• Foundation of skin• Attaches skin to underlying muscle and bone • Contains loose and adipose tissue• Contains ½ of body’s fat• Body fat for females 20-23%, males 13-25%

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Skin Color and Variations• Determined by:

- pigments - genetics- blood circulation- thickness of stratum corneum

• Melanocytes of darker skinned people produce more and darker melanin than fairer skinned people

• All races have same number of melanocytes

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Skin Pigments• Melanin:

- produced by melanocytes

- ranges from yellow to reddish-brown to black

- responsible for hair and eye color

- provides protection against UV light

- amt. produced determined by genetics, UV light, hormones

- freckles are accumulation of melanin

- albinism is absence of melanin

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• Carotene:

- yellow-orange pigment found in plants

- accumulates in stratum corneum

• Hemoglobin:

- gives pinkish-red color

- found in red blood cells

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Tanning and Sunburns

• Exposure to UV light stimulates melanocytes to increase production of melanin

• Melanin builds up to help protect skin against UV radiation (tan)

• A sunburn is the skin reacting to UV exposure• UV light causes elastic fibers to clump and become leathery• UV light can alter DNA in cells causing them to mutate

(cancer)

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Skin Color and Disease

• Redness:fever, hypertension, inflammation, allergies

• Pallor:anemia or low blood pressure

• Jaundice:liver disorder (yellow)

• Bronzing:Addison’s disease (kidney disease)

• Bruising:broken blood vessels

HairHair

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Hair Components

• Hair/shaft:

flexible strands of keratinized cells

• Root:

below skin (scalp)

HairHair shaft

Keratinocytes

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• Hair Bulb:

- base of root

- where hair is produced

• Hair Follicle:

- group of cells that surround root and bulb

- gives hair different shapes

Histology of Hair FollicleEpidermis

Hair follicle

Hair

Sebaceous gland

Hair FollicleMedium Magnification

Cortex of hair

Differentiationzone of hair

Hair matrix

Connectivetissuesheath

Glassymembrane

External root

sheath

Internal root

sheath

Dermis

Connective tissue sheath

Glassy membrane

External root sheath

Internal root sheath

Hair matrix

Dermal papilla

Hair Follicle High Magnification

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How is Hair Produced?• Hair is produced in hair bulb

• Hair bulb rests on blood vessels to supply it with nutrients

• Hair grows longer as cells are added to base of

hair bulb

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Hair Facts• Testosterone and good nutrition promote hair growth

• Growth occurs in cycles: active and resting

• Scalp hair grows for 3 years and rests for 1 year

• Eyelashes grow for 30 days and rest for 105 days

• We lose about 90 scalp hairs/day

• Grey hair is the loss or fading of melanin

• Male pattern baldness is from the loss of the hair follicle

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Hair Muscles• Arrector Pili:

- smooth muscle that surrounds each hair follicle

- contracts and hair stands on end

(goose bumps)

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Glands• Sebaceous glands:

- connected to hair follicle

- sebum: oily substance that lubricates hair and

skin to prevent drying

• Eccrine sweat glands:

- all over body and open into sweat pores

- water and salt secretions

Sebaceous GlandLow MagnificationEpidermis

Hair follicle

Arrector pili m. Sebaceous gland and duct

Sebaceous gland

Epidermis

Sweat gland

Sebaceous Gland High Magnification

Sebaceous gland

Duct of sebaceous gland

Hair follicle

Basal cell of sebaceous gland

Secretory cells

Eccrine Sweat GlandLow MagnificationEpidermis

Dermis

Hypodermis

Eccrine sweat gland and duct

Eccrine sweat gland

Duct of eccrine sweat gland

Eccrine Sweat GlandHigh Magnification

Eccrine sweat gland

Lumen of sweat gland

Epithelial cells of sweat gland

Myoepithelial cells

Basal lamina of eccrine sweat gland

Duct of Sweat GlandHigh Magnification

Epidermis

Dermis

Duct of sweat gland

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• Apocrine sweat glands:

- open into hair follicle

- only in armpits and genitalia

- thick, rich secretions

- become active during puberty and causebody odor

Apocrine Sweat GlandLow Magnification

Apocrine sweat gland

Epithelium

Lumen

Apocrine Sweat GlandHigh Magnification

Apocrine sweat gland Lumen Epithelial cells Myoepthelial cells

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Eccrinesweat gland

Sebaceous gland

Arrector pili(smooth muscle)

Duct of eccrinesweat gland

Sweat pores

Apocrinesweat gland

Hair bulb

Hair follicle

Duct ofapocrinesweat gland

Nails

• What are they?

thin plate with layers of dead stratum corneum cells with hard keratin

Nails

Free edge Nail body Eponychium

Nail root Nail matrix

Nail Structure

• Nail body:

visual part

• Nail root:

covered by skin

• Cuticle:

stratum corneum that extends into nail body

• Nail matrix:

- continuation of nail root

- gives rises to most of nail• Nail bed:

attaches to nail and is distal to nail matrix• Lunula:

- part of nail matrix

- whitish, crescent shaped area

- base of nail

Vitamin D Production

1. UV light causes skin to produce a precursor

molecule of vitamin D2. Precursor is carried by blood to liver where it is modified3. Next to kidneys where it is modified again to form active

vitamin D• Vitamin D can also be ingested through fish oils, fortified

milk, eggs, and butter.• Vitamin D stimulates intestine to absorb calcium and

phosphate (bone growth and muscle function)

Temperature Regulation

• Body temp. should be 98.6oF• Rate of chemical reactions (metabolism) is altered by

changes in temp.• To cool body:

blood vessels in dermis dilate and heat is transferred from deep in tissues to skin and sweat is produced

• To heat body:

blood vessels constrict to reduce blood flow to skin and heat is retained

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Aging and the Integument

• Blood flow decreases and skin becomes thinner due to decreased amounts of collagen

• Decreased activity of sebaceous and sweat glands make temperature regulation more difficult

• Loss of elastic fibers cause skin to sag and wrinkle

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Classification of Burns• 1st degree:

- damages only epidermis

- redness, slight swelling, pain

- heals within 2-3 days (usually no scar)

- includes sunburns or exposure to cold

• 2nd degree:

- damages epidermis and upper dermis

- redness, swelling, pain, blisters

- heals in 2 weeks with some scarring

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• 3rd degree:

- destroys epidermis and dermis

- burned areas are cherry red to black

- nerve endings are destroyed

- skin graft might be necessary

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Full-thickness

Third-degree

Subcutaneoustissue

Dermis

Epidermis

Second-degree

Partial-thickness

First-degree

Skin Cancer• Most common cancer• Mainly caused by UV light exposure• Fair-skinned people more prone • Prevented by limiting sun exposure and using

sunscreens • UVA rays cause tan and is associated with malignant

melanomas• UVB rays cause sunburns• Sunscreens should block UVA and UVB rays

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Types of Skin Cancer• Basal cell carcinoma:

- cells in stratum basale affected

- cancer removed by surgery

• Squamous cell carcinoma:

- cells above stratum basale affected

- can cause death

• Malignant melanoma:

- arises from melanocytes in a mole

- rare type

- can cause death

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(c)(b)(a)© Thomas B. Habif